sonography of 2/3 trimester Flashcards
What does the sonographer determine after fetal position is conceptiualized?
Left and right side of fetus
What is the suggested protocol?
survey of uterus, cervix, LUS and adnexa
fetal cardiac activity
fetal position
placental location
AFI 4 quadrants
anatomy survey of fetus
perform biometric measurements of fetus
Why is it important to constantly be aware of the left and right side of the fetus?
to correctly assess fetal anatomy and situs
What are the different fetal presentations?
oblique
transverse lie
breech
vertex (cephalic)
What are the different kinds of breech postions?
Complete breech
incomplete breech (one foot down into the pelvis)
frank breech (both feet up by the face, butt into the pelvis
What are the longitudinal presentations?
longitudinal lie - cephalic presentation (head down)(aka vertex)
longitudinal lie breech presentation (head up)
What are the transverse presentations?
head - maternal left, spine toward mom’s head
head - maternal right, spine toward mom’s feet
What are some ways to keep track of fetal left and right?
if fetal stomach lies on fetal left side, then you can determine left and right based on the position of the stomach
gallbladder on right side and APEX of heart pointing toward fetal left side…verified by their relationship to the stomach
What is the roll of the placenta?
to permit exhange of oxygenated maternal blood with deoxygenated fetal blood
maternal vessels coursing posterior to placenta circulate blood into placenta
blood from fetus reaches this point through the umbilical cord
what is PCI?
Placenta Cord Insertion
What is AFI?
amniotic fluid index
allows fetus to move freely within amniotic cavity
maintains intrauterine pressure and protects developing fetus from injury
umbilical cord and membranes, lungs, skin, and kidneys all contribute to production of amniotic fluid
What accounts for most of the total volume of amniotic fluid by second half of pregnancy?
fetal urination into amniotic sac
quantity of fluid is directly related to ______
kidney function
fetus
what structure is critically dependent on exhange of amniotic fluid within ______
normal lung development
lungs
When does the volume of amniotic fluid increase until which week?
34th then slowly diminishes
must be aware of relative differences in amniotic fluid volume throughout pregnancy
fluid surrounding fetus should be readily apparent
In the normal fetal brain parenchyma appears ______
hypoechoic
small size reflectors and high water content in tissue
slucus and gyrus more echogenic
What brain structures do we need to take pictures of?
cerebellum
choroid plexus
cisterna magna
lateral cerebral ventricles
midline falx
cavum septum pellucidi (CSP)
what are the midline structures?
interhemispheric fissure,
midline falx,
falx cerebri -
observed as membrane separting brain into two equal hemispheres
What is the fetal ventricular system?
consists of
two paried lateral ventricles,
midline third ventricle,
fourth ventricle adjacent to cerebellum
what does the ventricular system contain?
CSF - cerebral spinal fluid
How do you measure the ventricle?
locate atrium
measure directly across posterior portion
measure perpendicular to long axis of ventricle rather than the falx
place calipers at junction of ventricular wall and lumen or cavity of ventricle
What will fill lateral ventricle in normal pregnancy?
glomus or body of choroid plexus
What is the widest transverse diameter of the skull?
biparietal diameter - BPD
this is the proper level to measure the BPD and the HC
What is one way to proceed systematically through assessment and measurement of the fetus?
by moving from fetal head to feet obtaining anatomy images and measurement at each level
When there is severe oligohydraminos present, inadequate lung development occurs. What is the fetus at high risk for?
developing small or hypoplastic lungs
Branches of what artery run within the midline sulci and may be seen to pulsate within echogenic structures?
anterior cerebral artery
Why is the midline falx important landmark to visualize?
because its presence implies that separation of cerebrum has occured
What is it within the lateral ventricles that produces CSF?
choroid plexus tissue
where is choroid plexus tissue located?
within roofs of each ventricle except at frontal ventricular horns
In the lateral ventricles, what does a normal atrium measure? this is very important to know…
6.5 mm
if atrium measures >10mm it warrants serial imaging and further evaluation
What might the fetus have if the gloms appears to float or dangle within the ventricle cavity?
it is a sign of abnormally enlarged or dilated ventricles
VENTRICULOMEGALY
What are frontal horns?
frontal horns of ventricles are seen as two diverging echo-free structures within the frontal lobes of brain
When are the frontal horns prominent?
in the presence of ventricular dilation
what is the corpus callosum?
echogenic structure seen in transverse plane as a band of tissue between frontal ventricular horns.
How do you image the cerebral peduncles?
as transducer moves toward base of skull, heart-shaped cerebral peduncles imaged
similar in shape to thalamus but smaller
What artery is observed between lobes of peduncles at the interpeduncular cistern?
basilar artery
Where is the cerebellum located?
in back of cerebral peduncles within posterior fossa
what are the cerebellar hemispheres joined together by?
cerebellar vermis
why is it important to recognize usual configuration of cerebellum?
distortion my represent findings suggestive of OPEN SPINA BIFIDA
Where is the Cisterna magna located?
lies directly behind cerebellum
posterior fossa cistern filled with CSF
What does a normal appearing cisterna magna exclude?
almost all open spinal defects
The Cisterna magna is almost always effaced (thinned out) or obliterated in fetuses with what condition?
the Arnold-Chiari malformation changes associated with spina bifida
When you are evaluating the nuchal skin fold, what other anatomy will be in the plane where you will measure the thickness?
CSP
Cerebellum
Cisterna Magna
What is the normal thickness of the nuchal skin fold up to 20 weeks gestation?
5mm or less
What are fetuses with thickened nuchal skin at an increased risk for?
aneuploidy
What is aneuploidy?
a condition in which the chromosome number is not an exact multiple of the number characteristic of a particular species
an extra or missing chromosome
What cavity lies between the thalami?
the third ventricle
in the same scanning plane, box shaped CSP observed anterior to thalamus
What position does the fetus need to be in order for the orbital distances to be measured?
occipitoposterior position (fetal orbits directed up)
in this view orbital rings, lens, nasal structures may be demonstrated
What two planes are the orbits observed and measured in?
coronal scan: posterior to glabella-alveolar line
transverse scan: at level below BPD (along orbitomeatal line)
What is the IOD measurement?
inner orbital distance
medial border of orbit to opposite medial orbit
What is the OOD?
outer orbital or binocular distance
lateral border on one orbit to opposite lateral wall
What are you assessing in the profile view?
contour of frontal bone
nose
upper and lower lips
chin
What are some abnormalities you may seen in the forehead?
anterior cephaloceles
abnormal slopes
frontal bossing
abnormally small chin (MICROGNATHIA)
The coronal view of the face will help you see what craniofacial anomalies?
cleft lip
When you take an abdominal circumference what needs to be in the picture?
Left Portal Vein
spine
stomach
What is the sonographer required to document concerning the ACI (abdominal cord insertion)?
the ACI site and number of vessels in the umbilical cord
What does the normal human umbilical cord contain?
one umbilical vein
two umbilical arteries
Which vessel in the umbilical cord transports oxygenated blood from the placenta?
umbilical vein
What do the paired umbilical arteries do ?
return deoxygenated blood from iliac arteries of fetus to placenta for purification
Where should the umbilical cord be identified?
at cord insertion into placenta
at junction of cord into fetal umbilicus
What surrounds the arteries that spiral with larger umbilical vein?
Wharton’s jelly (material that supports the cord)
If the cord is seen on both sides of fetal neck, what can you used to visualize nuchal cord or encirclement of cord around fetal neck?
color doppler
multiple loops of nuchal cord have been identified with color doppler
What does 3VC mean?
3 vessel cord
What plane is the diaphragm commonly viewed in?
longitudinal plane
What shunts blood away from fetal lungs?
DUCTUS ARTERIOSUS
how does fetal circulation run?
fetal circulation shunts oxygenated blood arriving from placenta away from abdomen directly to heart and then to brain
How does the hepatobiliary system function fro shunting oxygen-rich blood arriving from the placenta?
directly to heart through DUCTUS VENOSUS
What anatomy changes after the baby is born?
the foramen ovale, ductus venosus and ductus arteriosus CLOSE
What carries oxygen-rich blood from the umbilical vein directly to IVC, which empties directly into the right atrium?
ductus venosus
How does IVC blood flow through the heart?
from right atrium through left atrium by way of FORAMEN OVALE
Where does the less oxygenated blood from the superior vena cava and small portion from IVC empty into?
right atrium and into right ventricle
Both ventricles pump blood into systemic circulation at the same time…true or false?
true
Where does blood ejected from the left ventricle flow to?
ascending aorta and to fetal brain
How does oxygenated blood get to the abdominal organs?
from rt ventricle, blood courses from pulmonary artery into DUCTUS ARTERIOSUS and through descending aorta
Why is the left lobe of the liver larger than the right lobe in the fetus?
because of larger quantity of oxygenated blood flowing through it
How is the liver discerned?
pebble gray
corresponding portal and hepatic vessels
When can small bowel be differentiated from large bowel?
beyond 20 weeks gestation
how are the large intestine with ascending, transverse, and descending colon and rectum identified?
by their peripheral locations in lower pelvis
how will the colon measure?
up to 20mm or larger as time of birth nears
may contain meconium particles
What is greater, the echogenicity of fetal bowel or fetal liver?
bowel
What is hyperechoic bowel?
when fetal bowel is as echogenic as fetal bone
has an associated risk for aneuploidy and neonatal/childhood pathology
How does the renal pelvis appear?
as an echo-free area in center of kidney
What are the abnormal measurements for the renal pelvis?
> 5mm before 20 GA
> 8MM between 20-30 weeks GA
> 10mm beyond 30 weeks GA
how often does a fetus void its bladder?
generally at least ONCE AN HOUR
failure to visualize bladder should prompt sonographer to recheck later for bladder filling
What should you suspect if you cannot identify urinary bladder in the presence of oligohydraminos?
renal abnormality
PROM
possible the bladder may not be full because of decreased ingestion of fluid
What planes is the longitudinal spine studied in?
coronal
sagittal
transverse
how many ossification points are there in each vertebra?
3
How many ossification points are seen on the spine in coronal and sagittal planes?
typically only 2
in sagittal section how does the spine appear?
two curvilinear lines extending from cervical spine to sacrum
In the normal fetus where does the spine taper? widen?
taper: near sacrum
widen: near base of skull
* double line appearance of spine referred to as RAILWAY SIGN - generated by echoes from posterior and anterior laminae and spinal cord
in the transverse plane, how many ossification points are visible?
3
spaced equidistant and spinal column appears as closed circle (indicating closure of neural tube)
What three echoes from circle or equilateral triangle?
represents center of vertebral body and posterior elements (laminae or pedicles)
Fluid filled fetal lungs are observed as solid, homogeneous masses of tissue, what borders them?
medially: heart
inferiorly: diaphragm
laterally: rib cage
The heart occupies the midline position within the chest. what would you want to exclude as reasons for its displacement?
possible mass of the lung
subdiaphragmatic herina
Why does the heart lie more transversely in the fetua than in an adult?
because the lungs aren’t inflated
What is the directionality of the apex, right ventricle and left atrium?
Apex: directed toward left anterior chest
Right ventricle: closest to chest wall
Left atrium: closest to spine
what technique will you use to view the 4 chamber heart?
angling cephalad after obtaining trv view of fetal abd that displays stomach
beam perpendicular to the septum
or
view with beam perpendicular to valves
What are you assessing when viewing the 4 chamber heart?
cardiac position, situs, axis
apex —->fetal left side
presence of right and left ventricle
What size do you want the ventricles of the heart to be?
equal size
by the end of pregnancy, why might the rt ventricle be larger than the left?
because its the chamber that pumps blood through ductus arteriosus to descending Ao and to placenta
When you identify presence of equal sized right and left atria, what do you want to see opening toward the left atrium as blood shunted from right atrium bypasses the lungs?
foramen ovale
What should appear uninterrupted in the heart?
interventricular septum
Septum appears _________ toward ventricles and _________as it courses cephalad within heart
wider
thins
What valves of the heart need to have normal placement?
tricuspid
mitral
How do you tell the tricuspid from the mitral valve?
tricuspid valve inserts lower or closer to apex than mitral valve
What should the valves should do what during diastole and systole?
diastole: open
systole: close
What is the normal heart rhythm?
120-160 bpm
What is FHR?
Fetal Heart Rate
What do you used to measure FHR?
m-mode
What is a short femur and short humerus associated with?
increased risk for aneuploidy
What issues are you looking for when you assess fetal bones?
measurements
anatomic configurations of individual bones
bowing
fractures
demineralization - seen in skeletal dysplasias
What is the normal cervix measurement in pregnancy?
3 cm or longer
When would you monitor and/or intervene when it comes to the cervix?
shortened
V shape
U shape
In what plane might you see female genitalia?
transverse plane
thighs and labia are identified _________ to bladder
ventral
How early can you possibly see male genitalia?
12th week
What is a common benign finding in male fetuses during intrauterine life?
fluid around testicles - HYDROCELE
How does a genetic sonogram differ from a normal anatomy scan?
includes all standard elements with special attention to “anatomy markers” for aneuploidy
What markers are typically elevated for aneuploidy?
nuchal fold
echogenic bowel
humerus/femur length
echogenic intracardiac foci (EIF)
renal pyelectasis
What is the risk for a 35 yr old woman entering a genetic sonogram?
1 in 200
if echogenic bowel is found - 1 in 33
if two or more markers documented - risk increased even more
